On going through the paperwork it seems there is no certificate of conformity for the LPG conversion and the vehicle is registered with dvla as being petrol and not LPG.

My question is this, can i get an inspection by a qualified fitter that will be able to produce a certificate of conformity or failing that an inspection document that will enable me to get it registered as LPG with dvla (for the cheaper road tax) and also that will satisfy my insurer?

I have phoned round a few lpg conversion companies and have been told different things.

You can get a safety check report done by an LPGA approved installer.This will satisfy the insurer and the DVLA.Some installers may issue a certificate but most will only supply you with an LPGA safety check report.The vehicle will only benefit from slightly cheaper road tax if it is registered after March 2001.
Where abouts are you?